1. Departement of Gastroenterology, Oslo University Hospital , Ullevål, Oslo , Norway
2. Institute of Clinical Medicine, University of Oslo , Oslo , Norway
3. Department of Medical Biochemistry, Oslo University Hospital , Radiumhospitalet , Norway
4. Faculty of Health Sciences, Oslo Metropolitan University , Oslo , Norway
5. Department of FOU and Gastroenterology, Østfold Hospital Trust , Kalnes , Norway